USB vs. Firewire External Hard Drive...

I know there has been several threads on externals, but I am wondering about USB vs Firewire.

Looking to pick up an external hard drive... Looking at either a Western Digital or a Seagate FreeAgent... the Western Digital is USB 2.0 and the Seagate is USB 2.0 and Firewire... the stats say that the Seagates USB transfer speed is actually faster than it's firewire speed... is this generally the case? Aside from saving a USB port is there a benefit to having both? If you have a USB/Firewire drive what mode do you use?

if i recall correctly, USB has a faster CONSTANT tranfer rate, and Firewire has a higher PEAK rate. how that applies to real life use, i honestly dont know. if you are using it for backup/storage, it honestly doesn't matter. if you are writing files directly to it from photosop or whatever, maybe go for firewire??